Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used for the treatment of inflammation, pain, and acute and chronic inflammatory disorders such as osteoarthritis and rheumatoid arthritis. These compounds are thought to work by inhibiting the enzyme cyclooxygenase (COX), which is also known as prostaglandin G/H synthase. COX catalyzes the conversion of arachidonic acid to prostaglandins.
Various forms of COX enzymes have been reported. They include a constitutive form known as COX-1, an inducible form known as COX-2 and the recently discovered COX-3, a variant of COX-1 that is inhibited by acetaminophen. COX-2 is inducible by mitogens, endotoxin, hormones, tumor promoters and growth factors. COX-1 is responsible for endogenous release of prostaglandins important for maintenance of gastrointestinal integrity and renal blood flow. Many of the side effects associated with NSAIDs are believed to be due to the inhibition of COX-1. Because of this, compounds that are selective for COX-2 have been developed and marketed. However, COX-2 inhibitors have been reported to cause dyspepsia, gastropathy and cardiovascular problems.
NSAIDs have also been used for cancer prevention and cancer treatment. The mechanism by which NSAIDs work in cancer treatment and cancer prevention may be related to COX overexpression. For example, some studies appear to indicate a link between COX expression and carcinogenesis. For example, cell lines that overexpress COX-2 are reported to be resistant to apoptosis, have increased invasiveness, and increased angiogenesis potential. Further, studies indicate that increased amounts of prostaglandins and COX-2 are commonly found in premalignant tissues and malignant tumors. Researchers have reported that COX-2 is up-regulated in several types of human cancers, including colon, pancreatic and breast.
Other studies report that the chemoprotective and antineoplastic properties of NSAIDs may occur in a COX-independent mechanism. For example, R-flurbiprofen is chemoprotective in the mouse model of intestinal polyposis and prostate cancer even though it does not have COX inhibitory activity. Similarly, sulindac sulfone, a metabolite of the NSAID sulindac, inhibits azoxy-methane-induced colon tumors in rats even though it does not have COX inhibitory activity. Further, NSAIDs can induce apoptosis in cancer cells that do not express COX-2 (Baek et al. 2001 Mol. Pharmacol. 59:901-908). The authors of these studies report that the chemoprotective and antineoplastic effects of NSAIDs occur via COX-dependent and COX-independent mechanisms.
β-catenin (also known as cadherin-associated protein) is a protooncogene in the downstream pathway of the wingless/frizzled (wnt/fzd) signaling pathway. Alterations in the pathways involved in regulating β-catenin are associated in the pathogenesis of many human cancers, including colorectal, desmoid (aggressive fibromatosis), endometrial, hepatocellular, leukemias, kidney, medulloblastoma, melanoma, ovarian, pancreatic, prostate, thyroid and uterine (Polakis, 2000 Genes Dev. 14:1837-1851; Chung et al. 2002 Blood 100:982-990).
β-catenin is reported to exist in at least three forms: membrane-bound (adherens complex), cytosolic, and nuclear. The nuclear accumulation of β-catenin, in concert with TCF/LEF proteins, induces downstream genes, including many genes implicated in tumorigenesis, for example, cyclin D1, and c-myc. The literature also reports that β-catenin is involved in the gene regulation of the androgen receptor, providing evidence for a role for the Wnt/β-catenin-TCF pathway for normal and neoplastic prostate growth (Amir et al., 2003, J. Biol. Chem. 278:30828-30834). The literature also reports that β-catenin may up-regulate COX-2 (Okamura et al., 2003, Cancer Res. 63:728-34).
β-catenin levels are reported to be regulated posttranslationally by the Wnt/fzd signaling pathway. In the absence of a Wnt signal, any β-catenin not bound to adherins is marked for degradation by a complex of proteins bound to β-catenin that includes glycogen synthase kinase-3β (GSK-3β), adenomatous polyposis coli (APC) protein, and axin. This complex facilitates the phosphorylation of β-catenin by GSK-3β and subsequent rapid degradation of β-catenin through proteasome degradation. Binding of Wnts to their receptors results in disruption of the β-catenin complex and inhibition of β-catenin degradation. This results in the accumulation of β-catenin in the cytoplasm and nucleus where it interacts with TCF/LEF proteins to regulate gene expression. Mutations in APC, β-catenin, or axin have been reported to increase the nuclear accumulation of β-catenin in cancers of epithelial origin.
The accumulation of β-catenin in the cytoplasm and nucleus has been reported in tumors with or without β-catenin mutations. In colorectal cancers, APC is mutated in 80% of all cases. In cases without APC mutations, β-catenin mutations are found in 50% of the cases. Accumulation of β-catenin is reported to occur in a very high percentage of cases in hepatoblastomas even though β-catenin is mutated in only 34% of the samples (Blaker et al., 1999 Genes Chromosomes Cancer 25:399-402). In hepatocellular carcinomas, β-catenin accumulation results from β-catenin mutations or axin mutation, but rarely APC mutations. Forty-two percent of samples in anaplastic thyroid demonstrate nuclear accumulation of β-catenin. Further, this high accumulation has been reported to correlate with a decrease in survival rate (Garcia-Rostan et al. 1999 Cancer Res. 59:1811-5). Rubinfeld et al. reported abnormal β-catenin regulation in 30% of melanoma cell lines (1997 Science 275:1790-2). Uterine endometriuim is reported to be associated with β-catenin accumulation in both samples that contain β-catenin mutations and samples without β-catenin mutations (Fukuchi et al. 1998 Cancer Res. 58:3526-3528.) Iwao et al. report that 63% of bone and soft-tissue tumors lacking a specific β-catenin mutation still demonstrate β-catenin accumulation (1999 Jpn. J. Cancer Res. 90:205-209).
Lin et al. reported that immunohistochemical analysis of cyclin D1 and β-catenin in breast tumors indicated that of 53 samples positive for cyclin D1, 49 of those were also β-catenin positive with β-catenin observed in both the nucleus and cytoplasm (2000 Proc. Natl. Acad. Sci. USA 97:4262-4266). A relationship between β-catenin and cyclin D1 has been reported for colon cancer and hepatocellular carcinoma (Tetsue et al. 1999 Nature 398:422-426; Ueta et al. 2002 Oncology Reports 9:1197-1203). Cyclin D1 is reported to be involved in the pathogenesis of squamous cell carcinoma (Xu et al. 1994 Int J. Cancer 59:383-387).
NSAIDs have been reported to affect β-catenin activity. For example, both aspirin and indomethacin have been reported to inhibit transcription of the β-catenin/TCF target cyclin D1 (Dihlmann et al. 2001 Oncogene 20:645-53). Sulindac was reported to decrease β-catenin in intestinal tumors from Min/+mice (McEntee et al. 1999 Carcinogenesis 20:635-640). Noda et al., report that etodolac increases the expression and cytoplasmic accumulation of cytoplasmic E-cadherin in Caco2 cells, but had no quantitative change in β-catenin expression (2002 J. Gastorenterol. 37(11):896-904).
Peroxisome proliferators-activated receptors (PPARs) are nuclear hormone receptors that have been reported to be involved in many cellular processes, including lipid metabolism and disease-related processes. PPARs form dimers with retinoid-X receptor and mediate their effects after ligand binding through gene transcription.
Three isoforms of PPAR are known to date—α, γ, and δ. PPARα is highly expressed in liver and has been reported to stimulate lipid metabolism. PPARγ is highly expressed in adipose tissue and is reported to be involved in activating adipogeneisis. PPARγ is reported to be involved in insulin resistance and a number of neoplastic processes including colorectal cancer. Shimada et al. hypothesize that activation of PPARγ signaling may compensate for deregulated c-myc expression in cells with mutated APC (2002 Gut 50:658-664). Ohta et al. report that a PPARγ ligand can cause a shift in β-catenin from the nucleus to the cytoplasm and induction of differentiation in pancreatic cancer cells (2002 Int J. Oncol. 21:37-42). PPARδ is expressed in many tissues and organs with the highest expression are brain, colon, and skin. Investigators have implicated PPARδ in cholesterol efflux, colon cancer, embryo implantation, preadipocyte proliferation and epidermal maturation. Investigators report that PPARδ is a downstream target of β-catenin/TCF-4 transcription complex (He et al., 1999 Cell 99:335-345). Also, PPARδ mRNA is reported to be overexpressed in many colorectal cancers.
NSAIDs have been reported to activate PPAR receptors (Lehmann et al. 1997 J Biol. Chem. 272:3406-3410). Researchers also report that NSAIDs may inhibit PPARδ, which might contribute to the chemoprotective effects of NSAIDs in preventing colorectal cancers (He et al. 1999).
Epidemiological studies indicate that NSAIDs may reduce or prevent the occurrence of Alzheimer's disease. A connection between the COX pathway and Alzheimer's disease has been reported and is mainly based on epidemiological studies. Studies indicate that Cox-2 is up-regulated in areas of the brain related to memory (Hinz et al. 2002 J. Pharm. Exp. Ther. 300:367-375). Weggen et al. report that some NSAIDs may reduce the pathogenic amyloid β peptide, Aβ42, by as much as 80% (2001 Nature 414:212-216). This reduction has been reported to occur in a COX-independent mechanism (Eriksen et al. 2002 J. Clinical Invest. 112:440-449). Eriksen also report that flurbiprofen and its enantiomers lower Aβ42 by targeting the γ-secretase complex that produces Aβ from amyloid β protein precursor. U.S. Pat. No. 6,255,347 discloses the use of R-ibuprofen for the treatment or prevention of Alzheimer's disease.
Analogs of etodolac are known in the art see, for example, U.S. Pat. Nos. 5,830,911; 5,824,699; 5,776,967; 5,420,289; 4,748,252; 4,686,213; 4,070,371; 3,939,178; and 3,843,681.
The use of etodolac and enantiomers of etodolac to treat cancer is described in U.S. Pat. Nos. 6,573,292; 6,545,034; and 5,955,504.
The use of NSAIDs to treat inflammation, cancer, and angiogenesis have been reported in the art see, for example, U.S. Pat. Nos. 5,972,986; 6,025,353; 5,955,504; and 5,561,151.